A fiber-reinforced thermoplastic-resin base made by impregnating a thermoplastic resin into continuous reinforcing fibers is excellent in specific strength and specific stiffness, high in weight reduction effect, and high in heat resistance and chemical resistance and, therefore, is preferably used for various applications such as transportation equipment such as aircraft, automobiles and the like, sports and electric/electronic parts. In recent years, due to the growing demand for weight reduction, replacement from metallic parts to resin parts, reduction in size and modularity of parts are progressing, mainly for aircraft and automobile applications and, therefore, development of materials is required to be more excellent in moldability and excellent in mechanical properties.
As a composite material for a structural material having excellent moldability and mechanical properties, for example, a fiber-reinforced thermoplastic-resin prepreg containing carbon fibers in a polyamide resin (for example, refer to JP-A-2013-159675) is known. Although such a prepreg is expected as a weight-reduction material to realize high mechanical properties to stably exhibit mechanical properties, it is necessary that the impregnation property of a matrix resin into portions between fiber bundles and reinforcing fibers uniformly disperse in the fiber-reinforced thermoplastic-resin base.
As a method of obtaining uniformity of the dispersion of reinforcing fibers, for example as described in JP-A-HEI 8-164521, a method is exemplified wherein a sectional image of a fiber-reinforced composite material is divided into sections each having an appropriate size and it is determined from a variation of the areal rates of reinforcing fibers in respective divided sections. In such a method, however, when reinforcing fibers are distributed, for example, as shown in FIG. 1, it is impossible to appropriately evaluate the density of reinforcing fibers in each section, and there is a possibility that in practice reinforcing fibers are dispersed in a nonuniform manner. Therefore, a fiber-reinforced thermoplastic-resin base with reinforcing fiber more uniformly dispersed is required.
Accordingly, it could be helpful to provide a fiber-reinforced thermoplastic-resin base with a thermoplastic resin as a matrix in which reinforcing fibers are more reliably uniformly dispersed and has a small variation in mechanical properties.